The present invention relates to a swimming fin and particularly to an improvement of the conventional swimming fin, with which the foot pack and the blade thereof are designed to join to each other as a structure capable of saving effort exerted by the wearer.
The swimming fin is one of indispensable facilities for the aquatics, especially the bed exercise. The principle of operating the swimming fin is that the wearer puts on the swimming fin with each foot respectively and a blade at the rear end of the swimming fin swings up and down to act on the water stream.
Accordingly, the structure of the swimming fin can be roughly divided into two parts, a foot pack being put on by a foot of the wearer and a water-bearing blade. The foot pack as the ordinary shoe is designed to have different sizes to comply with different soles in size. Basically, the size of a foot pack relates comfort of the wearer but it is no much relation with the forward force. The blade swinging up and down concerns the forward movement of the wearer so that the soft and flexible material is used for the blade. The blade is designed mostly in accordance with a shape of the tail fin of an ocean fish such as a whale or a stingray such that how to transmit the foot movement done by the wearer to the blade and to actuate smoothly with less effort is a key point pursued by the designer.
It is known by the experienced wearer that movements of a swimming fin include a down kick and an up kick. The down kick is a movement, which is to press water, for generating a forward moving force so that it is necessary to press downward with a full force. Considering the foot of the wearer bearing the force upward, the up kick force can be smaller so that the up kick is not required to produce a push force like the down kick. That is, the push force produced during up kick is about 60xcx9c70% of the push force during down kick.
The conventional swimming fin sold in the market is seldom to utilize the entire water-bearing cross section of the blade so that it needs great effort exerted by the user but it is unable to obtain a push force equivalent to the great effort. Alternatively, a blade with a greater area is the only way to do in order to obtain a greater push force while in use. Thus, a greater force has to be exerted by the user naturally.
U.S. Pat. Nos. 4,795,385, 5,304,081 and 6,159,064 are prior references, which are aimed to improve the design of the swimming fin and obtain more or less effects advantageously.
The crux of the present invention is to provide a swimming fin, which includes a foot pack and a blade. The foot pack has a space therein for being inserted with a sole of a wearer. The blade extends from the foot pack with a flat shape. It is characterized in that a root, which is disposed at an intersection of the foot pack and the blade, is formed by way of alternate arrangement of at lest a hard coil and at least a soft coil.